Sex-related variation in δ15N values of ground beetles (Coleoptera, Carabidae): A case study

Intersexual differences in food preferences and patterns of nutrient allocation are well known for a variety of animals, but this factor is not taken into account in the stable isotope-based studies of soil food webs. We used stable isotope composition of carbon and nitrogen (δ13C and δ15N values) to address the intersexual differences in the trophic niche of 27 species of ground beetles sampled in Northern Poland and Western Russia. Despite a high level of intra- and interspecies variation, males were, on average, enriched in 15N relative to females by 0.5 ± 0.1‰. Observed enrichment was most pronounced among species with high δ15N values and among spring breeding species collected in June. We did not find significant sex-related differences in δ13C values. Our results indicate sex-specific patterns in resource allocation or foraging behavior of predatory Carabidae during the breeding season.